The present invention relates to flame resistant graft polymer-modified polycarbonate moulding compositions containing phosphorus compounds and specially prepared fluorinated polyolefins, which compositions exhibit excellent flame retardancy and very good mechanical properties such as notched impact strength, elongation at break and very good stress cracking behaviour.
Diphosphates are known as flame retardant additives. JP 59 202 240 describes the production of such a product from phosphorus oxychloride, diphenols such as hydroquinone or bisphenol A and monophenols such as phenol or cresol. These diphosphates may be used as flame retardants in polyamide or polycarbonate. However, this document makes no reference to improved stress cracking resistance due to the addition of the oligomeric phosphate to polycarbonate moulding compositions.
EP-A 363 608 describes flame resistant polymer blends prepared from aromatic polycarbonate, copolymer or graft copolymer containing styrene together with oligomeric phosphates as flame retardant. It is mentioned in general terms that tetrafluoroethylene polymers may be added.
EP-A 0 767 204 describes flame resistant polyphenylene oxide (PPO) or polycarbonate mixtures which contain a mixture of oligophosphates (of the bisphenol A (BPA) oligophosphate type) and monophosphates as the flame retardant. Elevated flame retardant contents give rise to disadvantageous mechanical properties (notched impact strength, stress cracking behaviour) and reduced heat resistance.
EP-A 0 611 798 and WO 96/27600 describe moulding compositions which, in addition to polycarbonate, contain oligomeric, terminally alkylated phosphoric acid esters of the BPA type. Due to the alkylation, elevated contents are required in order to achieve effective flame retardancy, which is highly disadvantageous for many applicational properties (mechanical properties, heat resistance).
EP-A 0 754 531 describes reinforced PC/ABS moulding compositions which are suitable for precision components. Flame retardants which are used also include inter alia BPA type oligophosphates. The elevated filler contents have a highly disadvantageous effect on mechanical properties, such as elongation at break or notched impact strength.
EP-A 771 851 describes moulding compositions which contain aromatic polycarbonate; graft polymer based on diene rubber, SAN copolymer, a phosphate and tetrafluoroethylene polymers, wherein the polycarbonate has differing molecular weights. Resistance to loss of impact strength, to heat and moisture is stated as the advantage.
EP-A 755 977 describes polymer blends prepared from aromatic polycarbonate, graft copolymer having a rubber content of  less than 25% as well as oligomeric phosphates having an added content of  less than 8% and an N value of N=1-35 as flame retardant additives. Serious disadvantages with regard to flame retardancy may be expected due to the limitation of the content of phosphates as the flame retardant.
EP-A 747 424 describes thermoplastic resins which contain phosphate compounds having a molecular weight of approx. 500 to 2000 and of phosphate compounds having a molecular weight of approx. 2300 to 11000 as the flame retardant, wherein numerous thermoplastic resins are listed. The elevated molecular weights of the flame retardants may cause disadvantages relating to flame retardancy in this case too.
The object of the present invention is to provide flame retardant, graft polymer-modified PC moulding compositions which are distinguished by very good mechanical properties, elevated flame retardancy and very good stress cracking behaviour combined with elevated heat resistance. These moulding compositions are thus in particular suitable for those applications in which contact with special media, such as for example solvents, lubricants, cleaning agents, may occur.
It has now been found that graft polymer-modified polycarbonate moulding compositions which contain phosphorus compounds and special preparations of fluorinated polyolefins exhibit the desired range of properties.
The present invention accordingly provides graft polymer-modified polycarbonate moulding compositions containing phosphorus compounds of the formula (I) 
in which
R1, R2, R3 and R4 are mutually independently C1-C8 alkyl, optionally substituted by halogen, C5-C6 cycloalkyl, C6-C10 aryl or C7-C12 aralkyl, each optionally substituted by halogen and/or alkyl,
n are mutually independently 0 or 1,
q are mutually independently 0, 1, 2, 3 or 4,
N is 0.9 to 10, preferably 0.95 to 5, in particular 1 to 3,
R5 and R6 mutually independently mean C1-C4 alkyl, preferably methyl, or halogen, preferably chlorine and/or bromine,
Y means C1-C7 alkylidene, C1-C7 alkylene, C5-C12 cycloalkylene, C5-C12 cycloalkylidene, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO, xe2x80x94SO2xe2x80x94 or xe2x80x94COxe2x80x94,
and fluorinated polyolefins in the form of a coagulated mixture or as a precompound.